ISO 15184:2012 specifies a method for determining the film hardness by pushing pencils of known hardness over the film. The test can be performed on a single coating of a paint, varnish or related product, or on the upper layer of a multi-coat system. This rapid test has not been found to be useful in comparing the pencil hardness of different coatings. It is more useful in providing relative ratings for a series of coated panels exhibiting significant differences in pencil hardness. The method is applicable only to smooth surfaces.